Twitching is a British term used to mean “the pursuit of a previously-located rare bird.” In North America it is more often called “chasing”, though the British usage is starting to catch on there, especially among younger birders.

The term twitcher is reserved for those who travel long distances to see a rare bird that would then be ticked, or checked off, on a list.

The term originated in the 1950s, when it was used to describe the nervous behaviour of Howard Medhurst, a British birdwatcher. Prior terms for those who chased rarities were pot-hunter, tally-hunter, or tick-hunter. The main goal of twitching is often to accumulate species on one’s lists. Some birders engage in competition to accumulate the longest species list. The act of the pursuit itself is referred to as a twitch or a chase. A rare bird that stays put long enough for people to see it is twitchable or chase able.

The terms birding and birdwatching are today used by some interchangeably, although many participants prefer birding, both because it does not exclude the auditory aspects of enjoying birds, and because it does not have some associated negative connotations. (?)

At the most basic level, the distinction is one of dedication or intensity. Generally, self-described birders are more versed in minutiae like identification (aural and visual), molt, distribution, migration timing, and habitat usage. Whereas these dedicated birders may often travel specifically in search of birds, birdwatchers have been described by some enthusiasts as having a more limited scope, perhaps not venturing far from their own yards or local parks to view birds.